Subject: bug#59328: 29.0.50; `seq-keep' implementation only valid for lists

From: Michael Heerdegen <[email-masked]>
Date: Fri, 25 Nov 2022 10:47:31 +0100

Eli Zaretskii <[email-masked]> writes:

> Can tests for this be written in a way that they are only run if the
> relevant packages are available on the user's system?  If so, I'd
> prefer to have that than no tests at all.

I don't know.

Alternatively we could implement `seq-map' for an ad-hoc defined
sequence type and test using that type, e.g. this expression:

#+begin_src emacs-lisp
(progn
  (defvar gensym)
  (let ((gensym (make-symbol "foo")))
    (eval `(cl-defmethod seq-map (function (thing (head ,gensym)))
             (append (list (car thing) (cadr thing)) (seq-map function (cddr thing))))
          t)
    (equal (list gensym nil 4 46)
           (seq-keep (lambda (x) (and (integerp x) (* 2 x)))
                     (list gensym nil 2 'x gensym 23)))))
#+end_src

returns t with my patch installed and nil else and works without relying
on something external.  I'm not sure if defining methods (for seq-map in
this case) that are globally visible is allowed in tests, so I
implemented the example above in a way that the change of the generic
function is not visible from the outside (thus the "secret" gensym).

Would something like that be acceptable?

Sorry for my ignorance, I didn't write much tests before.

TIA,

Michael.